Development of a method to form a photo resist film having high precise and uniform thickness of the order of 100μm.

When forming thick photoresist film with a thickness of the order of 100 μm, which is used for microchannel fabrication, bubbles are easily contained by the resist layer. To remove these bubbles, the ambient air is vacuumed during the pre-baking process to vaporise the solvent contained by the resist before exposure. As the result of the suitable treatment, the bubbles can be completely removed. To obtain a thick photo resist film having a prescribed thickness, a previously developed remediation method is improved adopting an OHP film as the materials contacting with the photo resist.